The present invention relates to the testing of materials and, more particularly, to apparatus and methods for testing of samples by exposure of same to oscillating fluids.
The invention described herein was made in the course of work under a grant or award from the Department of Health, Education, and Welfare.
In the broad field of materials testing, it is known to repetitively actuate, stretch, flex, bend, or otherwise stress various materials, valves, components and other objects to determine durability, dependability and otherwise determine their suitability for particular applications. Thus, a type of durability testing is to cause the repetitive stressing of an object under test until fatigue causes failure thereof.
However, in certain kinds of test applications, it is desirable to isolate the test sample from the environment. Certain materials or devices which, during normal use, are exposed to certain fluids, will not be accurately tested if merely flexed or operated in a normal atmospheric environment. Desirably, such samples, if they are to be given truly representative durability (fatigue) tests, should be tested while immersed in a fluid to which they would be exposed in normal use.
A particular need arises in the durability-fatigue testing of biological tissue prosthetic heart valves. To be tested properly, such heart valves should be conducted in a sterile human blood plasma environment at normal body temperature, 37.degree. C.
Accordingly, it is an object of the present invention to provide an improved apparatus for materials testing, and, more paticularly, to provide a system for making closed durability (fatigue) tests.
A further object of the invention is the provision of such apparatus and methods of testing of various samples, including without limitation elastic materials, valves, components, and other objects.
A further object of the invention is the provision of such apparatus and methods for testing of prosthetic heart valves in a sterile blood plasma, or other body fluid environment at body temperature.
Another object of the invention is the provision of such testing apparatus and methods for carrying out the testing of a sample under test, whether such be a material, valve, component, or the like, in a preselected fluid medium.
Yet another object of the invention is the provision of such testing apparatus and methods which provide repetitively stressing or operation at a high frequency, such as much greater than that at which the sample under test would be flexed in normal use, thereby greatly shortening the life testing of the sample.
A further object of the invention is the provision of such testing apparatus and methods which allow a plurality of samples to be tested at one time.
A still further object of the invention is the provision of such testing apparatus and methods which greatly minimizes test volume while requiring very little input power.
Among still other objects of the invention may be noted the provision of such testing apparatus and methods which are mechanically simple; which provide a wide range of testing conditions, including different temperatures, pressures, frequencies, stresses; which are extremely reliable in operation; and which avoid improper testing conditions.
Further objects of the invention include the provision of testing apparatus which provides testing in a completely sealed fluid environment; which provides extreme economy of use of fluids; which provides very high test versatility and ease of insertion and removal of test samples; which provides high accessibility as well as visibility of test samples; in which test fluid is easily filled or emptied; and which is easily cleaned.
Among other objects of the invention are the provision of such apparatus which exposes test fluid to extremely limited surface areas, and which areas of the apparatus provides little friction of test fluid with consequent negligible heating of fluid.
Other objects and features will be in part apparent and in part pointed out hereinbelow.